lm317 variable power supply

[rehanessa]

in the design 2200uf capacitor has been used. is there any specific reason for that? Any calculation to justify this value?what will be the effect on circuit if i make it say 100u

secondly, two of the three capacitors used in the design are electrolytic while one is not. why so?

Project Link: http://www.electronics-lab.com/projects/power/010/index.html

 

[ante1]

Hi rehanessa,

The circuit is calculated for a peak current of 1.5A and the 2200uF capacitor will keep the ripple within a reasonable value. If you use a 100uF instead the ripple would rise to an unacceptable level. The non-electrolytic capacitor is to prevent self oscillation in the regulator, the low value is not standard in electrolytic caps.

 

[rehanessa]

now i wish to replace lm317 by lm338(5A max current ) and modify the circuit for 5A peak current. now what would happen to the 2200uf capacitor.
there should be some formula,calculations etc to evaluate the correct value of this capacitor.

also i could not understand what you mean by "self oscillating in regulator" can you please clear it for me?

 

[ante1]

I would recommend 10000uF or at least 6800uF for 5A peak current. Self-oscillating is the result of the regulator